C++primer5的code

/* * This file contains code from "C++ Primer, Fifth Edition", by Stanley B. * Lippman, Josee Lajoie, and Barbara E. Moo, and is covered under the * copyright and warranty notices given in that book: * * "Copyright (c) 2013 by Objectwrite, Inc., Josee Lajoie, and Barbara E. Moo." * * * "The authors and publisher have taken care in the preparation of this book, * but make no expressed or implied warranty of any kind and assume no * responsibility for errors or omissions. No liability is assumed for * incidental or consequential damages in connection with or arising out of the * use of the information or programs contained herein." * * Permission is granted for this code to be used for educational purposes in * association with the book, given proper citation if and when posted or * reproduced.Any commercial use of this code requires the explicit written * permission of the publisher, Addison-Wesley Professional, a division of * Pearson Education, Inc. Send your request for permission, stating clearly * what code you would like to use, and in what specific way, to the following * address: * * Pearson Education, Inc. * Rights and Permissions Department * One Lake Street * Upper Saddle River, NJ 07458 * Fax: (201) 236-3290 */ #include <cstddef> #include <iostream> #include <string> using std::cout; using std::cin; using std::endl; using std::string; using std::size_t; #include <bitset> using std::bitset; int main() { bitset<32> bitvec(1ULL); // 32 bits; low-order bit is 1, // remaining bits are 0 bool is_set = bitvec.any(); // true, one bit is set bool is_not_set = bitvec.none(); // false, one bit is set bool all_set = bitvec.all(); // false, only one bit is set size_t onBits = bitvec.count(); // returns 1 size_t sz = bitvec.size(); // returns 32 bitvec.flip(); // reverses the value of all the bits in bitvec bitvec.reset(); // sets all the bits to 0 bitvec.set(); // sets all the bits to 1 cout << "bitvec: " << bitvec << endl; sz = bitvec.size(); // returns 32 onBits = bitvec.count(); // returns 1, // i.e., the number of bits that are on // assign 1 to even numbered bits for (int index = 0; index != 32; index += 2) bitvec[index] = 1; // equivalent loop using set operation for (int index = 0; index != 32; index += 2) bitvec.set(index); // bitvec is unchanged bitset<32> b2 = ~bitvec; // b2 is a copy of bitvec with every bit flipped // assign value of last bit in bitvec to the first bit in b2 b2[0] = bitvec[bitvec.size() - 1]; bitvec[0] = 0; // turn off the bit at position 0 bitvec[31] = bitvec[0]; // give last bit the same value as the first bitvec[0].flip(); // flip the value of the bit at position 0 ~bitvec[0]; // equivalent; flips the bit at position 0 bool b = bitvec[0]; // convert the value of bitvec[0] to bool b2[0] = ~bitvec[0]; // first bit in b2 has the opposite value // of the first bit in bitvec unsigned i = 0; if (bitvec.test(i)) // bitvec[i] is on ; //equivalent test using subscript if (bitvec[i]) // bitvec[i] is on ; cout << "bitvec: positions turned on:\n\t"; for (int index = 0; index != 32; ++index) if (bitvec[index]) cout << index << " "; cout << endl; // equivalent; turn off first bit bitvec.flip(0); // reverses the value of the first bit bitvec.set(bitvec.size() - 1); // turns on the last bit bitvec.set(0, 0); // turns off the first bit bitvec.reset(i); // turns off the ith bit bitvec.test(0); // returns false because the first bit is off bitvec[0] = 0; bitvec.flip(0); // reverses value of first bit bitvec[0].flip(); // also reverses the first bit cout << "new inits" <<endl; // bits13 is smaller than the initializer; // high-order bits from the initializer are discarded bitset<13> bits13(0xbeef); // bits are 1111011101111 // bits20 is larger than the initializer; // high-order bits in bits20 are set to zero bitset<20> bits20(0xbeef); // bits are 00001011111011101111 // on machines with 64-bit long long 0ULL is 64 bits of 0, // so ~0ULL is 64 ones, so 0 ... 63 are one, and 64 ... 127 are zero // if long long has 32 bits, 0 ... 32 are one, 33 ... 127 are zero bitset<128> bits128(~0ULL); cout << "bits13: " << bits13 << endl; cout << "bits20: " << bits20 << endl; cout << "bits128: " << bits128 << endl; cout << "bits20[0] " << bits20[0] << endl; cout << "bits20[19] " << bits20[19] << endl; // bitvec1 is smaller than the initializer bitset<32> bitvec1(0xffff); // bits 0 ... 15 are set to 1; // 16 ... 31 are 0 // bitvec2 same size as initializer bitset<64> bitvec2(0xffff); // bits 0 ... 15 are set to 1; // 16 ... 63 are 0 // assuming 64-bit long long, bits 0 to 63 initialized from 0xffff bitset<128> bitvec3(0xffff); // bits 32 through 127 are zero cout << "bitvec1: " << bitvec1 << endl; cout << "bitvec2: " << bitvec2 << endl; cout << "bitvec2[0] " << bitvec2[0] << endl; cout << "bitvec2[31] " << bitvec2[31] << endl; cout << "bitvec3: " << bitvec3 << endl; // pre C++ 11 has a constructor from string but not from const char* bitset<32> bitvec4(string("1100")); // bits 2 and 3 are 1, all others are 0 cout << "strval: " << "1100" << endl; cout << "bitvec4: " << bitvec4 << endl; string str(string("1111111000000011001101")); bitset<32> bitvec5(str, 5, 4); // four bits starting at str[5], 1100 bitset<32> bitvec6(str, str.size()-4); // use last four characters cout << "str: " << str << endl; cout << "bitvec5: " << bitvec5 << endl; cout << "str: " << str << endl; cout << "bitvec6: " << bitvec6 << endl; unsigned long ulong = bitvec3.to_ulong(); cout << "ulong = " << ulong << endl; bitset<32> bitvec7 = bitvec1 & bitvec4; cout << "bitvec7: " << bitvec7 << endl; bitset<32> bitvec8 = bitvec1 | bitvec4; cout << "bitvec8: " << bitvec8 << endl; bitset<16> chk(string("111100110011001100000")); cout << "chk: " << chk << endl; bitset<16> bits; cin >> bits; // read up to 16 1 or 0 characters from cin cout << "bits: " << bits << endl; // print what we just read return 0; }